The videos from NDC 2011 are now online, including my talk Developing .NET Applications for the Mac App Store (direct link). You can also download a printable version of my presentation. Hopefully there will be an official torrent of the videos soon, because there were plenty of other sessions that are worth seeing. Thanks to everyone who helped make it such a great conference!
Correction: In the presentation I said that native objects don't retain references to managed objects, which is incorrect. The problem I intended to refer to is a common coding error where views are retained but their controllers are not, e.g.